Method and device for configuring improved drx scheme for connected terminals in wireless communication system

ABSTRACT

Provided are a method and a device for configuring control plane (C-plane) discontinuous reception (DRX) in a wireless communication system. A base station configures C-plane DRX for terminals only having an activated C-plane transmitted/received via a cellular network and indicates the presence or absence of signaling to be transmitted to one or more awake terminals in the C-plane DRX. Also provided are a method and a device for extending an on-duration according to C-plane DRX in a wireless communication system. A terminal receives C-plane DRX configuration information and a mobile terminating (MT) signaling indicator and temporarily extends an on-duration for the DRX of a C-plane according to the C-plane configuration information and MT signaling indicator.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is the National Stage filing under 35 U.S.C. 371 of International Application No. PCT/KR2015/010955, filed on Oct. 16, 2015, which claims the benefit of U.S. Provisional Application No. 62/067,951 filed on Oct. 23, 2014, the contents of which are all hereby incorporated by reference herein in their entirety.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates to wireless communication and more specifically, a method and a device for configuring an improved discontinuous reception (DRX) scheme for connected user equipments (UEs) in a wireless communication system.

Related Art

With the recent trend of increasing high-rate data traffic, fifth generation mobile communication technologies are in discussion for their realistic and efficient backup. One of requirements for fifth generation mobile communication technologies is the interworking between heterogeneous wireless communication systems, particularly between a cellular system and a wireless local area network (WLAN) system. The cellular system may be one of a 3rd generation partnership project (3GPP) long-term evolution (LTE) system, a 3GPP LTE-A (advanced) system, and an institute of electrical and electronics engineers (IEEE) 802.16 (WiMax, WiBro) system. The WLAN system may be an IEEE 802.11 (Wi-Fi) system. In particular, WLAN is a wireless communication system that is commonly used for various user equipments, and thus, the cellular-WLAN interoperation is a high-priority convergence technique. Offloading by the cellular-WLAN interoperation may increase the coverage and capacity of the cellular system.

In other words, the fifth-generation mobile communication system may use multiple RATs in a converging manner through the interoperation between heterogeneous wireless communication systems. Each entity in the plurality of RATs constituting a fifth-generation mobile communication system may exchange information therebetween, and accordingly, the optimal communication system may be provided to a user in the fifth-generation mobile communication system. Among the plurality of RATs constituting the fifth-generation mobile communication system, a specific RAT may operate as a primary RAT system, and another specific RAT may operate as a secondary RAT system. That is, the primary RAT system may mainly play a role to provide a communication system to a user in the fifth-generation mobile communication system, while the secondary RAT system may assist the primary RAT system. In general, a 3GPP LTE(-A) or IEEE 802.16 cellular system with relatively broad coverage may be a primary RAT system, and a Wi-Fi system with relatively narrower coverage may be a secondary RAT system.

Discontinuous reception (DRX) is a method used for conserving the battery of a user equipment (UE) by turning off its receiver when the UE does not detect data. DRX improves signaling task and user experience considerably since it may quickly start the receiver with a minimum amount of signaling.

A wireless communication system in which cellular/Wi-Fi system are tightly coupled may require improved DRX.

SUMMARY OF THE INVENTION

The present invention provides a method and a device for configuring an improved discontinuous reception (DRX) scheme for a connected user equipment (UE) in a wireless communication system. The present invention provides a method and a device for configuring control plane (C-plane) DRX newly defined for a UE in a radio resource control (RRC) connected state in a wireless communication system where a cellular system and a Wi-Fi system is combined with each other.

In an aspect, a method for configuring a control plane (C-plane) discontinuous reception (DRX) by an evolved NodeB (eNB) in a wireless communication system is provided. The method includes configuring the C-plane DRX for user equipments (UEs) having only an activated C-plane transmitted and received via a cellular network, and indicating whether signaling to be transmitted is present or not to one or more UEs awakened in the C-plane DRX.

In another aspect, a method for extending an on-duration according to a control plane (C-plane) discontinuous reception (DRX) by a user equipment (UE) in a wireless communication system is provided. The method includes receiving C-plane DRX configuration information and a mobile terminating (MT) signaling indicator, and extending the on-duration of the C-plane DRX temporarily according to the C-plane configuration information and the MT signaling indicator.

An efficient DRX scheme may be configured for UEs having only the C-plane in the cellular network.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a cellular system.

FIG. 2 shows a wireless local area network (WLAN) system.

FIG. 3 shows an example of a scenario of a converged communication system of a cellular system and a Wi-Fi system.

FIG. 4 shows an example of tightly coupled cellular/Wi-Fi network.

FIG. 5 shows an example of DRX operation.

FIG. 6 shows another example of DRX operation.

FIG. 7 shows another example of DRX operation.

FIG. 8 shows an example of the existing DRX operation.

FIG. 9 shows an example of DRX operation according to an embodiment of the present invention.

FIG. 10 shows an example of how DRX operates according to a fixed MT signaling indicator according to an embodiment of the present invention.

FIG. 11 show an example of how DRX operates according to a dynamic MT signaling indicator according to an embodiment of the present invention.

FIG. 12 shows another example of how DRX operates according to a dynamic MT signaling indicator according to an embodiment of the present invention.

FIG. 13 shows another example of how DRX operates according to a dynamic MT signaling indicator according to an embodiment of the present invention.

FIG. 14 shows another example of how DRX operates according to a dynamic MT signaling indicator according to one embodiment of the present invention.

FIG. 15 shows an example of a method for configuring a C-plane DRX according to an embodiment of the present invention.

FIG. 16 shows an example of a method for extending an on-duration according to C-plane DRX according to an embodiment of the present invention.

FIG. 17 shows a wireless communication system to implement an embodiment of the present invention.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

A technology below can be used in a variety of wireless communication systems, such as code division multiple access (CDMA), frequency division multiple access (FDMA), time division multiple access (TDMA), orthogonal frequency division multiple access (OFDMA), and single carrier frequency division multiple access (SC-FDMA). CDMA can be implemented using radio technology, such as universal terrestrial radio access (UTRA) or CDMA2000. TDMA can be implemented using radio technology, such as global system for mobile communications (GSM)/general packet radio service (GPRS)/enhanced data rates for GSM evolution (EDGE). OFDMA can be implemented using radio technology, such as IEEE 802.11(Wi-Fi), IEEE 802.16(WiMAX), IEEE 802-20, or Evolved UTRA (E-UTRA). IEEE 802.16m is the evolution of IEEE 802.16e, and it provides a backward compatibility with an IEEE 802.16e-based system. UTRA is part of a universal mobile telecommunications system (UMTS). 3rd generation partnership project (3GPP) long term evolution (LTE) is part of evolved UMTS (E-UMTS) using evolved-UMTS terrestrial radio access (E-UTRA), and it adopts OFDMA in downlink (DL) and SC-FDMA in uplink (UL). LTE-A (advanced) is the evolution of 3GPP LTE.

LTE-A and IEEE 802.11 are chiefly described as an example in order to clarify the description, but the technical spirit of the present invention is not limited to LTE-A and IEEE 802.11.

FIG. 1 shows a cellular system. Referring to FIG. 1, the cellular system 10 includes one or more base stations (BSs) 11. The BSs 11 provide communication services to respective geographical areas (in general called ‘cells’) 15 a, 15 b, and 15 c. Each of the cells can be divided into a number of areas (called ‘sectors’). A user equipment (UE) 12 can be fixed or mobile and may be referred to as another terminology, such as a mobile station (MS), a mobile terminal (MT), a user terminal (UT), a subscriber station (SS), a wireless device, a personal digital assistant (PDA), a wireless modem, or a handheld device. In general, the BS 11 refers to a fixed station that communicates with the UEs 12, and it may be referred to as another terminology, such as an evolved-NodeB (eNB), a base transceiver system (BTS), or an access point.

The UE generally belongs to one cell. A cell to which a UE belongs is called a serving cell. A BS providing the serving cell with communication services is called a serving BS. The cellular system includes other cells neighboring a serving cell. Other cells neighboring the serving cell are called neighbor cells. A BS providing the neighbor cells with communication services is called as a neighbor BS. The serving cell and the neighbor cells are relatively determined on the basis of a UE.

This technology can be used in the downlink (DL) or the uplink (UL). In general, DL refers to communication from the BS 11 to the UE 12, and UL refers to communication from the UE 12 to the BS 11. In the DL, a transmitter may be part of the BS 11 and a receiver may be part of the UE 12. In the UL, a transmitter may be part of the UE 12 and a receiver may be part of the BS 11.

FIG. 2 shows a wireless local area network (WLAN) system. The WLAN system may also be referred to as a Wi-Fi system. Referring to FIG. 2, the WLAN system includes one access point (AP) 20 and a plurality of stations (STAs) 31, 32, 33, 34, and 40. The AP 20 may be linked to each STA 31, 32, 33, 34, and 40 and may communicate therewith. The WLAN system includes one or more basic service sets (BSSs). The BSS is a set of STAs that may be successfully synchronized with each other and may communicate with each other, and does not mean a specific region.

An infrastructure BSS includes one or more non-AP stations, APs that provide a distribution service (DS), and a DS that links a plurality of APs with each other. In the infrastructure BSS, an AP manages non-AP STAs of the BSS. Accordingly, the WLAN system shown in FIG. 2 may include an infrastructure BSS. In contrast, an independent BSS (IBSS) is a BSS that operates in ad-hoc mode. The IBSS does not include an AP and thus lacks a centralized management entity. That is, in the IBSS, the non-AP STAs are managed in a distributed manner. The IBSS may have all the STAs constituted of mobile STAs and is not allowed to access the distribution system, thus achieving a self-contained network.

The STA is random functional medium that includes a physical layer interface for a wireless medium and an media access control (MAC)) observing IEEE 802.11 standards, and in its broader concepts, it includes both the AP and non-AP station.

The non-AP STA is an STA, not an AP. The non-AP STA may also be referred to as a mobile terminal, a wireless device, a wireless transmit/receive unit (WTRU), a user equipment (UE), a mobile station (MS), a mobile subscriber unit or simply as a user. Hereinafter, for ease of description, the non-AP STA denotes an STA.

The AP is a functional entity that provides access to a distribution system via a wireless medium for an STA associated with the AP. In the infrastructure BSS including an AP, communication between STAs is basically done via an AP, but in case a direct link is established, direct communication may be achieved between STAs. The AP may also be referred to as a central controller, a base station (BS), a NodeB, a base transceiver system (BTS), or a site controller.

A plurality of infrastructure BSSs may be linked with each another through a distribution system. The plurality of BSSs linked with each another is referred to as an extended service set (ESS). The APs and/or STAs included in the ESS may communicate with each other, and in the same ESS, an STA may move from one BSS to another, while in seamless communication.

FIG. 3 shows an example of a scenario of a converged communication system of a cellular system and a Wi-Fi system.

It is assumed in FIG. 3 that the cellular system operates as a primary RAT system of the converged communication system, and the Wi-Fi system operates as a secondary RAT system of the converged communication system. Further, the cellular system may be a 3GPP LTE(-A) system. Hereinafter, for ease of description, it is assumed that the primary RAT system of the converged communication system is a 3GPP LTE(-A) system, and the secondary RAT system of the communication system is an IEEE 802.11 system, i.e., a Wi-Fi system. However, embodiments of the present invention are not limited thereto.

Referring to FIG. 3, there are a plurality of general devices 61, 62, 63, 64, and 65 in the coverage of the cellular base station 50. Each of the general devices 61, 62, 63, 64, and 65 may be a user equipment in a cellular system. The cellular base station 50 may communicate with each of the general devices 61, 62, 63, 64, and 65 via a cellular radio interface. For example, the cellular base station 50 may perform voice call communication with each of the general devices 61, 62, 63, 64, and 65 or may control access of each general device 61, 62, 63, 64, and 65 to a Wi-Fi system.

The cellular base station 50 is connected to a serving gateway (S-GW)/mobility management entity (MME) 70 through a cellular system interface. The MME contains a user equipment's access information or information on a user equipment's capability, and such information may be mainly used for mobility management. The MME is in charge of a control plane. The S-GW is a gateway having an E-UTRAN as an end point. The S-GW is in charge of a user plane. The S-GW/MME 70 is connected to a packet data network (PDN) gateway (P-GW) 71 and a home subscriber server (HSS) 72 through the cellular system interface. The PDN-GW is a gateway having a PDN as an end point.

The P-GW 71 and the HSS 72 are connected to a 3GPP access authentication authorization (AAA) server 73 through the cellular system interface. The P-GW 71 and the 3GPP AAA server 73 may be connected to an evolved packet data gateway (ePDG) 74 through the cellular system interface. The ePDG 74 may be included only in un-trusted non-3GPP access. The ePDG 74 may be connected to a WLAN access gateway (WAG) 75. The WAG 75 may be in charge of a P-GW in a Wi-Fi system.

Meanwhile, a plurality of APs 81, 82, and 83 may be present in the coverage of the cellular base station 50. Each of the APs 81, 82, and 83 may have coverage which is shorter than that of the cellular base station 50. Each of the APs 81, 82, and 83 may communicate with general devices 61, 62, and 63 that are present in its coverage through a Wi-Fi radio interface. In other words, the general devices 61, 62, and 63 may communicate with the cellular base station 50 and/or APs 81, 82, and 83. Communication methods of the general devices 61, 62, and 63 are as follows:

1) Cellular/Wi-Fi simultaneous radio transmission: the general device 61 may perform high-speed data communication with the AP 81 through a Wi-Fi radio interface while communicating with the cellular base station 50 through a cellular radio interface.

2) Cellular/Wi-Fi user plane automatic shift: the general device 62 may communicate with one of the cellular base station 50 and the AP 82 by user plane automatic shift. At this time, the control plane may be present in both the cellular system and the Wi-Fi system or only in the cellular system.

3) Terminal cooperative transmission: the general device 64 operating as a source device may directly communicate with the cellular base station 50 through a cellular radio interface or may indirectly communicate with the cellular base station 50 through a general device 65 operating as a cooperative device. That is, the cooperative device 65 may assist the source device 64 so that the source device 64 may indirectly communicate with the cellular base station 50 through itself. The source device 64 and the cooperative device 65 communicate with each other through a Wi-Fi radio interface.

4) Wi-Fi-based cellular link control mechanism: the AP 83 may perform a cellular link control mechanism such as paging or location registration of a network for the cellular general device 63. The general device 63 is not directly connected to the cellular base station 50 and may indirectly communicate with the cellular base station 50 through the AP 83.

Each of the APs 81, 82, and 83 is connected to the WAG 75 through a Wi-Fi system interface.

FIG. 4 shows an example of tightly coupled cellular/Wi-Fi network. Referring to FIG. 4, in the tightly coupled cellular/Wi-Fi network, a BS of the cellular network is connected to the P-GW and PDN through S-GW/MME as shown in FIG. 3. Meanwhile, an AP is connected to the BS and connected to the P-GW and PDN through the same interface as the BS. This configuration is different from the embodiment of FIG. 3 where an AP is connected to the P-GW through WAG. In other words, in the tightly coupled cellular/Wi-Fi network, the BS and the AP are collocated or connected to each other.

In the tightly coupled cellular/Wi-Fi network, the cellular network should oversee mobility of UEs to ensure seamless data transmission. This is so because in the tightly coupled cellular/Wi-Fi network, the cellular network does not have coverage holes. Table 1 shows the roles of the cellular network and the Wi-Fi network in the tightly coupled cellular/Wi-Fi network.

TABLE 1 Cellular network Wi-Fi network Role of C-plane User mobility None Data session management Network resource control (off-loading) Role of U-plane Data transmission and Data transmission and reception reception Connection Always On demand

Referring to Table 1, in the tightly coupled cellular/Wi-Fi network, control plane (C-plane) is provided only for the cellular network but is not provided for the Wi-Fi network. In other words, even if data is transmitted and received only on the user plane (U-plane) of the Wi-Fi network, the UE and the cellular network transmit and receive control signals on the C-plane. Also, since priority of C-plane signaling transmission is high (radio resource control (RRC) message=1, non-access stratum (NAS) message=3), the UE always has to maintain the RRC_CONNECTED state with the cellular network. Therefore, power consumption of the UE is increased, leading to degradation of energy efficiency.

In what follows, discontinuous reception (CRX) is described.

FIG. 5 shows an example of DRX operation. Referring to FIG. 5, a UE is turned on only for on-duration of the DRX cycle (namely, activity state) and is turned off for the remaining period of the cycle (namely, inactivity state). Also, after successfully decoding the physical downlink control channel (PDCCH) over the on-duration, the UE stays in the active state while an inactivity timer operates. Table 2 shows various parameters used for the DRX operation.

TABLE 2 DRX parameter Description DRX Cycle Specifies the periodic repetition of an active state that lasts for on-duration On Duration Specifies how many subframes the UE should be timer in active state when a new DRX cycle starts. DRX Inactivity Specifies how many PDCCH subframes after timer successfully decoding a PDCCH the UE must remain active. DRX Specifies the maximum number of consecutive retransmission PDCCH subframes the UE should remain active timer to wait an incoming retransmission after the first available retransmission time. DRX short cycle Specifies the periodic repetition of an active state when the UE is under short DRX condition, it's a sort of discontinuous inactivity timer DRX short cycle Specifies the consecutive number of subframes timer the UE shall follow the short DRX cycle after the DRX Inactivity Timer has expired longDRX- = drxStartOffset CycleStartOffset)

FIG. 6 shows another example of DRX operation. Referring to FIG. 6, on-duration is configured within a long DRX cycle, and hybrid automatic repeat request (HARQ) timer is configured. While the HARQ timer operates, HARQ may be performed.

FIG. 7 shows another example of DRX operation. Referring to FIG. 7, when the UE satisfies the short DRX condition, on-duration is configured within the long DRX cycle, and a short DRX cycle is additionally configured. The UE performs DRX according to the short DRX cycle while the short DRX cycle timer operates, and performs DRX according to the long DRX cycle when the short DRX cycle is completed.

DRX reduces power consumed in a UE but is disadvantageous in that the UE is unable to know existence of signaling or data transmitted to the UE. In other words, the UE has to decode all of the PDCCHs to figure out existence of radio resources allocated to the UE in the on-duration. The aforementioned feature of DRX operation may be inefficient particularly for a UE having only the C-plane in the cellular network pf the tightly coupled cellular/Wi-Fi system. In other words, in case only the C-plane exists in the cellular network of a tightly coupled cellular/Wi-Fi network, occurrence of signaling is hard to predict and occurrence frequency may be low. Messages that may be transmitted on the C-plane may include a bearer context modification/deactivation message, NAS message such as a dedicated EPS bearer context activation message, RRC connection reconfiguration message, and neighbor measurement configuration message according to attenuation of strength of a cellular/Wi-Fi signal. In other words, it is highly probable that this kind of signaling may not be transmitted. On the other hand, priority given to such signaling may be high. For most cases, the priority of an RRC message is 1, and that of a NAS message is 3. Therefore, it may not be preferable to set a large number to the DRX cycle.

Therefore, to solve the problem of the existing DRX operation, a new DRX scheme may be proposed according to an embodiment of the present invention. In what follows, the DRX scheme newly defined according to an embodiment of the present invention is denoted as a light DRX or C-plane DRX. In what follows, the light DRX and C-plane DRX may be used interchangeably. According to an embodiment of the present invention, light DRX may be applied only for the UE having only an activated C-plane transmitted and received via the cellular network in a tightly coupled cellular/Wi-Fi system, while the existing DRX method (long DRX and short DRX) may be applied to the UE having both of active C-plane and U-plane transmitted and received via the cellular network. Depending on the activity state of the UE, the UE may switch appropriately between the light DRX and existing DRX.

FIG. 8 shows an example of the existing DRX operation. Referring to FIG. 8, after the DRX inactivity timer starts operation, the UE enters either the short DRX or long DRX depending on the situation, and when the DRX short cycle timer expires in the short DRX, the UE enters the long DRX.

FIG. 9 shows an example of DRX operation according to an embodiment of the present invention. Referring to FIG. 9, after the DRX inactivity timer starts operation, the UE enters one of the short DRX, long DRX, or light DRX depending on the situation. When the DRX short cycle timer expires in the short DRX, the UE enters either the long DRX or the light DRX. Also, when the DRX long cycle expires in the long DRX, the UE enters the light DRX.

Table 3 shows various parameters for DRX operation according to an embodiment of the present invention.

TABLE 3 DRX parameter Description DRX Cycle Specifies the periodic repetition of an active state that lasts for on-duration On Duration Specifies how many subframes the UE should be in timer active state when a new DRX cycle starts. DRX Inactivity Specifies how many PDCCH subframes after timer successfully decoding a PDCCH the UE must remain active. DRX Specifies the maximum number of consecutive retransmission PDCCH subframes the UE should remain active to timer wait an incoming retransmission after the first available retransmission time. DRX short cycle Specifies the periodic repetition of an active state when the UE is under short DRX condition, it's a sort of discontinuous inactivity timer DRX short cycle Specifies the consecutive number of subframes the timer UE shall follow the short DRX cycle after the DRX Inactivity Timer has expired longDRX- = drxStartOffset CycleStartOffset) Light DRX Cycle Specifies the periodic repetition of an active state when the UE is under Light DRX condition Light DRX On Specifies how many subframes a UE should be in Duration timer active state when a light DRX cycle starts. The on-duration in a light DRX cycle may change automatically to a fixed value (e.g. 1 ms) instead of being delivered explicitly. DRX Long Cycle Specifies the consecutive number of subframes the Timer UE shall follow the long DRX cycle after the DRX Inactivity Timer has expired

Referring to Table 3, compared with Table 2, a Light DRX Cycle parameter, a Light DRX On Duration Timer, and a DRX Long Cycle Timer may be additionally configured. In other words, the UE may perform DRX operation according to the light DRX cycle when the UE satisfies the light DRX condition, and the on-duration may be configured additionally within a light DRX cycle. Also, a UE performing long DRX operation may enter the light DRX, when the DRX long cycle timer expires and the UE satisfies a light DRX condition. The light DRX condition may correspond to the UE having an active C-plane only transmitted and received via the cellular network.

The start point of the on-duration within a light DRX cycle may be determined by Equation 1.

[(SFN*10)+subframe number]modulo(light DRX cycle)==drxStartOffset  [Equation 1]

In what follows, described will be the case where signaling occurs when light DRX is applied to a UE having only an activated C-plane transmitted and received via the cellular network according to an embodiment of the present invention. According to an embodiment of the present invention, an eNB may inform one or more UEs awaken at the corresponding subframe and employing light DRX about existence of signaling to be transmitted. In what follows, an indicator indicating existence of signaling to be transmitted to a UE is called a mobile terminating (MT) signaling indicator. Two types of MT signaling indicators may be defined: fixed and dynamic indicator. A fixed indicator and a dynamic indicator may be applied at the same time. Also, one or more dynamic indicator types may be applied. In case an MT signaling indicator indicates existence of signaling to be transmitted to a UE, the on-duration may be extended. The on-duration may be extended only for a UE supposed to receive signaling, or the same on-duration timing may be extended to all of the unspecified UEs.

First, a fixed MT signaling indicator according to an embodiment of the present invention will be described. A fixed MT signaling indicator may be a newly defined physical MT-signaling indicator channel (PSICH). A PSICH may indicate existence of signaling to be transmitted to a UE. For example, if the value of the PSICH is 0, it may indicate that there is no signaling to be transmitted to a UE whereas, if the value of the PSICH is 1, it may indicate existence of signaling to be transmitted to a UE. Information about existence of PSICH and radio resource area allocated to the PSICH may be transmitted through PSICH configuration information. For example, PSICH configuration information may be transmitted through system information block (SIB). The radio resource area information allocated for the PSICH may include information about allocation time and/or resource area. The information about allocation time may be expressed in terms of system frame number (for example, even-numbered system frame, odd-numbered system frame, or all of the system frames) or subframe number. Information about resource area may be expressed in terms of the number of resource blocks and/or frequency offset.

FIG. 10 shows an example of how DRX operates according to a fixed MT signaling indicator according to an embodiment of the present invention. Referring to FIG. 10, for a UE employing light DRX (namely a UE having only an activated C-plane transmitted and received via the cellular network), the PSICH is transmitted over the on-duration. If the PSICH is 0 in the on-duration, all of the UEs employing light DRX transit to the sleep mode without decoding PDCCH in the common search space (CSS) and UE-specific search space (USS). If the PSICH is 1 in the on-duration, all of the UEs employing light DRX decode PDCCH and extend the on-duration temporarily. At this time, light DRX may be extended as long as set by the DRX inactivity timer or on-duration timer. Although FIG. 10 illustrates shows an example where on-durations of all of the unspecified UEs belonging to the same on-duration are extended, it is equally possible that only the on-duration of a UE supposed to receive signaling may be extended.

Described will be a dynamic MT signaling indicator according to an embodiment of the present invention. A dynamic MT signaling indicator may be transmitted by using multicast scheme. In case one or more UEs, among UEs employing light DRX and remaining in the on-duration at the corresponding subframe, are supposed to receive signaling from an eNB, a dynamic MT signaling indicator may be transmitted to the UEs in the on-duration at the corresponding subframe according to multicast scheme. A dynamic MT signaling indicator may indicate a UE identifier such as cell radio network temporary identifier (C_RNTI), start offset, and on-duration extension. The on-duration may start from the subframe corresponding to (current subframe number+start offset) according to the start offset. The on-duration extension is an interval made as the on-duration is temporarily extended, and an eNB may schedule signaling within the corresponding interval.

Also, an RNTI intended to indicate an MT signaling indicator may be newly defined for the dynamic signaling MT indicator. Table 4 shows RNTIs used for indicating an MT signaling indicator.

TABLE 4 Hexadecimal value RNTI 0000 N/A 0001-003C RA-RNTI, C-RNTI, semi-persistent scheduling (SPS) C-RNTI, temporary C-RNTI, TPC-PUCCH-RNTI and TPC-PUSCH-RNTI 003D-FFF3 C-RNTI, SPS C-RNTI, temporary C-RNTI, TPC-PUCCH-RNTI and TPC-PUSCH-RNTI FFF4-FFFC Reserved for later use FFFD MT signaling scheduling C-RNTI FFFE P-RNTI FFFF SI-RNTI

Referring to Table 4, when the RNTI value is 0xFFFD, C-RNTI for MT signaling scheduling may be indicated.

Meanwhile, the dynamic MT signaling indicator may be transmitted according to unicast scheme. In case a UE from, among UEs employing light DRX and remaining in the on-duration at the corresponding subframe, is supposed to receive signaling from an eNB, a dynamic MT signaling indicator may be transmitted to the corresponding UE at the corresponding subframe according to unicast scheme. The dynamic MT signaling indicator may indicate a start offset and on-duration extension. According to the start offset, the on-duration may start from the subframe corresponding to (current subframe number+start offset). The on-duration extension is an interval made as the on-duration is temporarily extended, and an eNB may schedule signaling within the corresponding interval.

Described will be how DRX operates according to a dynamic MT signaling indicator according to one embodiment of the present invention. Depending on the DRX operation scheme, it may be classified as type 0, type 1, or type 2.

In the type 0 DRX operation scheme, an eNB may transmit resource allocation information masked with an MT signaling scheduling C-RNTI or UE's C-RNTI through the PDCCH in the form of an existing DCI format. At this time, the MT signaling indicator itself may be transmitted through the resourced provided by the PDCCH (e.g. physical downlink shared channel (PDSCH)). In case resources can be allocated to a subframe corresponding to the on-duration (namely in case scheduling is possible), the eNB transmits signaling at the corresponding subframe. At this time, a PDCCH including radio resource information corresponding to the signaling may also be transmitted in the conventional manner. On the other hand, in case resource allocation to the subframe corresponding to the on-duration is not possible (namely in case scheduling is not possible), the eNB may inform the UE through an MT signaling indicator that there exists signaling to be transmitted although it is not scheduled at the corresponding subframe. A UE which has not received a PDCCH corresponding to its C-RNTI or MT signaling indicator in the on-duration transits to the sleep mode. A UE which has received the PDCCH corresponding to its C-RNTI in the on-duration operates in the conventional manner. A UE which has received an MT signaling indicator in the on-duration extends the on-duration temporarily.

FIG. 11 show an example of how DRX operates according to a dynamic MT signaling indicator according to an embodiment of the present invention. FIG. 11 shows a case in which the on-duration of the corresponding UE is extended temporarily in case the C-RNTI of the UE is 003D according to the type 0 DRX scheme. Referring to FIG. 11, a UE which has not received an MT signaling indicator corresponding to itself in the on-duration transits to the sleep mode. A UE which has received an MT signaling indicator corresponding to itself in the on-duration (namely C-RNTI=003D) extends the on-duration temporarily.

In the type 1 DRX scheme, decoding priority may be given according to a search space. The eNB may transmit an MT signaling indicator masked with an MT signaling scheduling C-RNTI through the PDCCH on the CSS by using the existing DCI format. First, a UE employing light DRX may decode the PDCCH on the CSS. Meanwhile, according to the number of UEs, a UE identifier may be used instead of the MT signaling indicator masked with the MT signaling scheduling C-RNTI. For example, according to the size limit of the DCI format, in case the number of UEs belonging to the same on-duration is large, the MT signaling indicator may be used, while the UE identifier may be used in case the number of UEs is small.

FIG. 12 shows another example of how DRX operates according to a dynamic MT signaling indicator according to an embodiment of the present invention. FIG. 12 shows a case in which the on-durations of all of the unspecified UEs at the same time point of the on-duration are extended according to the type 1 DRX scheme. Referring to FIG. 12, if failing to receive an MT signaling indicator in the on-duration, all of the UEs employing light DRX transit to the sleep mode without decoding the PDCCH on the USS. Receiving an MT signaling indicator in the on-duration, all of the UEs employing light DRX decode the PDCCH and extend the on-duration temporarily.

FIG. 13 shows another example of how DRX operates according to a dynamic MT signaling indicator according to an embodiment of the present invention. FIG. 13 shows a case in which the on-duration of a UE is extended temporarily in case the C-RNTI of the UE is 003D according to the type 1 DRX scheme. Referring to FIG. 13, the UE, if failing to receive an MT signaling indicator corresponding to itself in the on-duration, the UE transits to the sleep mode without decoding the PDCCH on the USS. The UE, if receiving an MT signaling indictor corresponding to itself in the on-duration, decodes the PDCCH and temporarily extends the on-duration.

In the type 2 DRX scheme, decoding priority may be given according to the DCI format. The eNB may transmit an MT signaling indicator masked with an MT signaling scheduling C-RNTI through the PDCCH by using a DCI format newly defined for the corresponding purpose. First, a UE employing light DRX may decode the PDCCH to which the corresponding DCI format is transmitted. Accordingly, in case on-durations of all of the unspecified UEs at the same time point of the on-duration are extended according to a dynamic MT signaling indicator, all of the UEs employing light DRX, if failing to receive an MT signaling indicator in the on-duration, transit to the sleep mode without decoding the PDCCH to which a different DCI format is transmitted. All of the UEs employing light DRX, if receiving an MT signaling indicator in the on-duration, decode the PDCCH to which a different DCI formation is transmitted and extend the on-duration temporarily.

FIG. 14 shows another example of how DRX operates according to a dynamic MT signaling indicator according to one embodiment of the present invention. FIG. 14 shows a case where the on-duration of a UE is temporarily extended when the C-RNTI of the corresponding UE is 003D according to the type 2 DRX scheme. Referring to FIG. 14, if a UE does not receive an MT signaling indicator corresponding to itself in the on-duration, the UE does not decode the PDCCH to which a different DCI format is transmitted and transits to the sleep mode. Receiving an MT signaling indicator corresponding to itself in the on-duration, the UE decodes the PDCCH to which a different DCI formation is transmitted and extends the on-duration temporarily.

FIG. 15 shows an example of a method for configuring a C-plane DRX according to an embodiment of the present invention.

In step S100, an eNB configures C-plane DRX for the UEs having only an activated C-plane transmitted and received via the cellular network. The C-plane DRX may be configured by such parameters as a light DRX cycle newly defined for the C-plane DRX, light DRX on-duration timer, and DRX long cycle timer.

In step S110, the eNB indicates whether signaling to be transmitted is present or not to one or more UEs awakened in the C-plane DRX. Indicating whether signaling to be transmitted is present or not to one or more UEs awakened in the C-plane DRX may include transmitting an MT signaling indicator to the one or more UEs. The MT signaling indicator may be a fixed MT signaling indicator, and the fixed MT signaling indicator may correspond to a PSICH. Information about existence of the PSICH and allocated radio resource area may be transmitted, and the corresponding information may include allocation time of the PSICH and resource area. Alternatively, the MT signaling indicator may be a dynamic MT signaling indicator. The dynamic signaling indicator may be indicated by multicast scheme, and at this time, an MT signaling scheduling C-RNTI corresponding to the dynamic MT signaling indicator may be defined. Alternatively, the dynamic MT signaling indicator may be indicated by unicast scheme. The dynamic MT signaling indicator may include at least one of a UE identifier, start offset, and on-duration extension.

FIG. 16 shows an example of a method for extending an on-duration according to C-plane DRX according to an embodiment of the present invention. In step S200, a UE having only an activated C-plane transmitted and received via the cellular network receives C-plane DRX configuration information and MT signaling indicator. In step S210, a UE temporarily extends the on-duration of C-plane DRX according to the C-plane configuration information and MT signaling indicator. The MT signaling indicator may be a fixed MT signaling indicator, and the C-plane DRX may be temporarily extended in case the fixed MT signaling indicator has a specific value. Alternatively, the MT signaling indicator may be a dynamic MT signaling indicator, and the C-plane DRX may be temporarily extended in case the DCI format is received from the eNB through the PDCCH by being masked with an MT signaling scheduling C-RNTI or C-RNTI of the UE. This corresponds to the type 0 DRX scheme described above. Alternatively, the MT signaling indicator may be a dynamic MT signaling indicator, and the C-plane DRX may be temporarily extended in case the DCI format including the dynamic MT signaling indicator is received from the eNB through the PDCCH on the CSS by being masked with the MT signaling scheduling C-RNTI. This corresponds to the type 2 DRX scheme described above. Alternatively, the MT signaling indicator may be a dynamic MT signaling indicator, and the C-plane DRX may be temporarily extended in case a new DCI format including the dynamic MT signaling indicator is received from the eNB through the PDCCH by being masked with the MT signaling scheduling C-RNTI. This corresponds to the type 2 DRX scheme described above.

FIG. 17 shows a wireless communication system to implement an embodiment of the present invention.

A BS 800 includes a processor 810, a memory 820, and a transceiver 830. The processor 810 may be configured to implement proposed functions, procedures, and/or methods in this description. Layers of the radio interface protocol may be implemented in the processor 810. The memory 820 is operatively coupled with the processor 810 and stores a variety of information to operate the processor 810. The transceiver 830 is operatively coupled with the processor 810, and transmits and/or receives a radio signal.

A UE 900 includes a processor 910, a memory 920, and a transceiver 930. The processor 910 may be configured to implement proposed functions, procedures, and/or methods in this description. Layers of the radio interface protocol may be implemented in the processor 910. The memory 920 is operatively coupled with the processor 910 and stores a variety of information to operate the processor 910. The transceiver 830 is operatively coupled with the processor 910, and transmits and/or receives a radio signal.

The processors 810, 910 may include application-specific integrated circuit (ASIC), other chipset, logic circuit and/or data processing device. The memories 820, 920 may include read-only memory (ROM), random access memory (RAM), flash memory, memory card, storage medium and/or other storage device. The transceivers 830, 930 may include baseband circuitry to process radio frequency signals. When the embodiments are implemented in software, the techniques described herein can be implemented with modules (e.g., procedures, functions, and so on) that perform the functions described herein. The modules can be stored in memories 820, 920 and executed by processors 810, 910. The memories 820, 920 can be implemented within the processors 810, 910 or external to the processors 810, 910 in which case those can be communicatively coupled to the processors 810, 910 via various means as is known in the art.

In view of the exemplary systems described herein, methodologies that may be implemented in accordance with the disclosed subject matter have been described with reference to several flow diagrams. While for purposed of simplicity, the methodologies are shown and described as a series of steps or blocks, it is to be understood and appreciated that the claimed subject matter is not limited by the order of the steps or blocks, as some steps may occur in different orders or concurrently with other steps from what is depicted and described herein. Moreover, one skilled in the art would understand that the steps illustrated in the flow diagram are not exclusive and other steps may be included or one or more of the steps in the example flow diagram may be deleted without affecting the scope and spirit of the present disclosure. 

What is claimed is:
 1. A method for configuring a control plane (C-plane) discontinuous reception (DRX) by an evolved NodeB (eNB) in a wireless communication system, the method comprising: configuring the C-plane DRX for user equipments (UEs) having only an activated C-plane transmitted and received via a cellular network; and indicating whether signaling to be transmitted is present or not to one or more UEs awakened in the C-plane DRX.
 2. The method of claim 1, wherein the C-plane DRX is configured by a light DRX cycle, a light DRX on-duration timer, and a DRX long cycle timer.
 3. The method of claim 1, wherein the indicating whether signaling to be transmitted is present or not to one or more UEs awakened in the C-plane DRX comprises transmitting an mobile terminating (MT) signaling indicator to the one or more UEs.
 4. The method of claim 3, wherein the MT signaling indicator is a fixed MT signaling indicator, and wherein the fixed MT signaling indicator corresponds to a physical MT-signaling indicator channel (PSICH).
 5. The method of claim 4, further comprising transmitting information on existence of the PSICH and allocated radio resource area.
 6. The method of claim 3, wherein the MT signaling indicator is a dynamic MT signaling indicator.
 7. The method of claim 6, wherein the dynamic MT signaling indicator is indicated by a multicast scheme, and wherein an MT signaling scheduling cell radio network temporary identifier (C-RNTI) corresponding to the dynamic MT signaling indicator is defined.
 8. The method of claim 6, wherein the dynamic MT signaling indicator is indicated by a unicast scheme.
 9. The method of claim 6, wherein the dynamic MT signaling indicator includes at least one of a UE identifier, a start offset, or an on-duration extension.
 10. A method for extending an on-duration according to a control plane (C-plane) discontinuous reception (DRX) by a user equipment (UE) in a wireless communication system, the method comprising: receiving C-plane DRX configuration information and a mobile terminating (MT) signaling indicator; and extending the on-duration of the C-plane DRX temporarily according to the C-plane configuration information and the MT signaling indicator.
 11. The method of claim 10, wherein the UE has only an activated C-plane transmitted and received via a cellular network.
 12. The method of claim 10, wherein the MT signaling indicator is a fixed MT signaling indicator, and wherein the C-plane DRX is temporarily extended if the fixed MT signaling indicator has a specific value.
 13. The method of claim 10, wherein the MT signaling indicator is a dynamic MT signaling indicator, and wherein the C-plane DRX is temporarily extended if a downlink control information (DCI) format is received from an evolved NodeB (eNB) through a physical downlink control channel (PDCCH) by being masked with an MT signaling scheduling cell radio network temporary identifier (C-RNTI) or C-RNTI of the UE.
 14. The method of claim 10, wherein the MT signaling indicator is a dynamic MT signaling indicator, and wherein the C-plane DRX is temporarily extended if a DCI format including the dynamic MT signaling indicator is received from an eNB through a PDCCH on a common search space (CSS) by being masked with an MT signaling scheduling C-RNTI.
 15. The method of claim 10, wherein the MT signaling indicator is a dynamic MT signaling indicator, and wherein the C-plane DRX is temporarily extended if a new DCI format including the dynamic MT signaling indicator is received from an eNB through a PDCCH by being masked with an MT signaling scheduling C-RNTI. 